Web hem method and apparatus for insuring a flat hem in a web

Details Web hem method and apparatus for insuring a flat hem in a web Web hem method and apparatus for insuring a flat hem in a web

1988-02-22

1989-04-25

Schmidt, Frederick R.

Manufacturing container or tube from paper; or other manufacturi

Container making

Pliable container

493225, 493928, 1562731, B31B 164

Patent

active

048244252

ABSTRACT:
A draw tape bag forming apparatus includes an edge folder for folding the edges of pliable plastic web to form a hem in the edge. A draw tape is fed into the open hem which is then heat sealed along the inner edge of the hem wall to form a tubular hem. The web is of an indefinite length and moves continuously through the machine. The heat sealed hem is an expanded air-filled type hem. An electrostatic generator unit is mounted downstream of the ballooned hem. The generator unit includes a charging bar mounted in spaced relation to reference ground plate to form a gap with the ballooned hem passing therebetween. The hem is aligned with the bar. A 120 volt power supply is connected to the charging bar and establishes a high voltage along the length of the bar. An electrostatic field is created across the gap and induces a charge in the walls of the hem the hem collapses against the ground plate to form a flat hem in the web for subsequent passing of the web through a bag making machine which seals and severs the web on longitudinally spaced lines to form the bags. The power supply may establish a negative voltage relative to the ground plate. The power supply may be directly connected to the bar and plate.

REFERENCES:
patent: 4182222 (1980-01-01), Stahl
patent: 4372798 (1983-02-01), Dalton
patent: 4419855 (1983-12-01), Shanklin
patent: 4624654 (1986-11-01), Boyd et al.
patent: 4664649 (1987-05-01), Johnson et al.

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